The present invention relates to a non-volatile memory device that stores resistance value information of a variable resistance element, which can be electrically rewritable, in a non-volatile manner.
Recently, as non-volatile memory devices, ReRAMs (Resistive Random Access Memory) that store resistance value information of an electrically-rewritable variable resistance element in a non-volatile manner have been attracted attention, and researches for the memory devices have been actively performed.
The variable resistance element as a memory element of the ReRAM is configured by an electrode/a metal oxide/an electrode. It is known that there are two types of operation principles in the variable resistance element. The operation principle of one type is for shifting between a high-resistance state and a low-resistance state by changing the polarity of an applied voltage, which is referred to as a bipolar type. The operation principle of the other type is for shifting between a high-resistance state and a low-resistance state by controlling the voltage value and the time period of the applied voltage, which is referred to as a non-polar type (or unipolar type).
In order to implement a high-density memory cell array, the unipolar type is preferable. The reason is that, in the unipolar type, a cell array can be configured by superposing a variable resistance element and a rectifying device such as a diode at each cross point of bit lines and word lines without using a transistor.
When the cross-point-type cell array is configured without using a rectifying element, write disturbance occurs for unselected cells due to crosstalk generated in a write operation. In order to reduce the influence, a technique for applying a write compensation voltage to the unselected memory cells after the application of the write voltage has been disclosed in JP-A-2006-344349.
On the other hand, in order to prevent crosstalk in the cross-point-type cell array, a rectifying device such as a diode is superposed with the variable resistance element (for example, see U.S. Pat. No. 6,831,854).
A cross-point-type cell array for which voltages having the same polarity can be used for the write and erase operations and a cross-point-type cell array for which a write operation is performed by using a short pulse and an erase operation is performed by using a long pulse are, for example, disclosed in Y. Hosoi et al, “High Speed Unipolar Switching Resistance RAM (RRAM) Technology” IEEE International Electron Devices Meeting 2006 Technical Digest p. 793˜796.
In the ReRAM, when gaps between the bit lines or the word lines decreases for implementing high-density and high integration, write disturbance (or erase disturbance) for unselected memory cells occurs due to capacitive coupling in a write (or erase) operation.